I'm learning economics, marketing and business as well and there are good resources online (although, that's true, I'm reading a few books as well, but it's the same for computer stuff in fact).

Among the resources I know and use are:

Paul Graham's essays, like many people here (I prefer reading them on paper anyway, but all of them are available on his website);

Joel Spolsky's blog (joelonsoftware.com) used to have very good articles (lately it's not as good as it used to be); he had the best of them published, too.

Eric Sink's blog (software.ericsink.com); great articles on marketing and business for geeks.

There are good articles about the basics of business in the Trizoko online business journal: http://www.trizle.com/trizoko

On changethis.com you'll find a lot of great PDFs on business subjects (very good resource; there is good stuff by Seth Godin here)

For economics, I'm reading the work of Frédéric Bastiat, available online here: bastiat.org.